1. Field of the Invention
The present invention generally relates to electric relay assemblies and, more particularly, to electromagnetic relay assemblies of a type having a test actuator for actuating the electromagnetic relay assembly to ascertain the operability thereof.
2. Description of the Prior Art
Electromagnetic relay assemblies of the type referred to above are well known in the art. The test actuator is generally used to ascertain the operability of the associated electromagnetic relay assembly, that is, to ascertain whether or not the associated electromagnetic relay assembly functions properly.
Two examples of prior art electromagnetic relay assemblies of the type referred to above are shown in side sectional and partially sectioned side views in FIGS. 3 and 4 of the accompanying drawings, respectively, reference to which will now be made for further discussion of the prior art.
The electromagnetic relay assembly shown in FIG. 3 comprises a generally rectangular or square base 1 including a generally L-shaped yoke 2 rigidly mounted thereon. The L-shaped yoke 2 has an upright portion 2a, secured at one end to the base 1, and an overhang portion 2b continued at one end to the opposite end of the upright portion 2a so as to extend perpendicular to the upright portion 2a and generally parallel to the base 1. An armature or electromagnet 3 having a core and a winding formed around the core has opposite poles and is secured at one of the poles rigidly to the upright portion 2a of the L-shaped yoke 2.
The illustrated relay assembly also comprises a movable iron bar 4 having one end pivotably connected to a free end of the overhang portion 2b of the L-shaped yoke 2, the opposite end of which is integrated together with a generally elongated movable contact member 6 by means of a retainer 5. The contact member 6 has one end remote from the retainer 5 formed with a movable contact element 6a selectively engageable with one of two fixed contact elements 7a and 7b that are mounted stationarily on the base 1. So far illustrated, the movable iron bar 4 together with the contact member 6 is normally biased so as to permit the movable contact element 6a to engage the fixed contact element 7a, such that when the armature 3 is electrically energized, the movable iron bat 4 can be magnetically attracted towards the adjacent pole of the armature 3 with the movable contact element 6a consequently switched from the fixed contact element 7a to the fixed contact element 7b.
While the above described assembly is encased in a generally cubic casing 9, the test actuator employed in the prior art relay assembly shown in FIG. 3 comprises a push rod 9 having an inner end operatively coupled with the retainer 5 and an outer end slidably extending through an opening 9a defined in a top wall of the casing 9. Therefore, when an external pushing force is applied to the outer end of the push rod 9, the applied push is transmitted to the retainer 5 causing the movable iron bar 4 to pivot counterclockwise as viewed in FIG. 3 about a point 4a of pivot with the movable contact element 6a consequently brought into engagement with the fixed contact element 7b. Whether or not the illustrated relay assembly does function properly can be ascertained in any known method, for example, by means of a testing instrument that may be connected electrically with the fixed contact elements 7a and 7b.
In the prior art electromagnetic relay assembly shown in FIG. 4, the test actuator comprises a headed push rod 8b having a head formed at the inner end thereof and held in contact with the retainer 5 while the outer end thereof extends axially slidably through an opening 9b that is defined in one of side walls forming the casing 9.
The relay assembly shown in FIG. 4 functions in a manner substantially similar to that shown in FIG. 3, except for a difference found in direction from which the external pushing force is applied to the push rod.
However, it has been found that any one of the prior art electromagnetic relay assemblies shown in and described with reference to FIGS. 3 and 4, respectively, is difficult to assembly to a final shape, involving a time-consuming and laborious effort which eventually results in not only an increase in manufacturing cost, but also a difficulty for the relay assembly to be assembled on an automated production line.
More specifically, the relay unit including the yoke carrying the movable electric contact member and the armature all in assembled state on the base is, after they have been assembled together, encased in the casing 9. The employment of the push rod forming a part of the test actuator and being a member separate and independent from the relay unit requires a cumbersome and time-consuming handling in order for it to be repositioned properly within the casing and relative to the relay unit. Even though the push rod is pivotally, but non-removably connected to the retainer or any other portion of the relay unit, an alignment of the outer end of the push rod with the opening in the casing as the relay unit is encased relatively into the casing is not easy to accomplish.
These inconveniences hitherto experienced during the fabrication of the relay assembly might have been successfully eliminated if that portion of the casing, which is aligned in position with the movable contact member, is so designed in any way as to be deformable inwardly of the casing to an extent that that portion of the casing can, when so deformed, drive the movable contact member for testing purpose. This is disclosed in, for example, the Japanese Laid-open Utility Model Publications No. 56-75434 and No. 60-186644, published Jun. 19, 1981, and Dec. 11, 1985, respectively.
According to the publication No. 56-75434, a wall portion of the casing which confronts the movable contact member is formed with a generally U-shaped slit so as to leave a deflectable or pliable tongue which, when deflected by the application of the external pushing force thereto, drives the movable contact member.
A deflectable or pliable tongue similar to that referred to above is also disclosed in the publication No. 60-186644, but the latter discloses a different structure of the relay unit. Specifically, the relay unit disclosed therein has only a pair of contact members which are connected together when the deflectable or pliable tongue are pushed inwardly of the casing. This is possible because of the use of an actuating lever having its opposite ends confronting the tongue and one of the contact members, respectively, a generally intermediate portion of which is pivotally supported by the free end of the yoke. Thus, the external push applied to the tongue can be transmitted to one of the contact member through the actuating lever.
While the design disclosed in any one of the last mentioned two publication is effective to eliminate the inconveniences encountered in the design shown in and described with reference to any one of FIGS. 3 and 4, a different problem has been found in that the interior of the casing is susceptible to a build-up of external dust which intrudes through the slit defining the deflectable or pliable tongue. This means that the electromagnetic relay assembly according to the two Japanese publications is limited in place of installation and may not be used in an environment full of dust and/or a substantial amount of moisture.
In view of the foregoing, the assignee of the present invention is in possession of the Japanese Laid-open Utility Model Publication No. 56-140127, published Oct. 23, 1981, and also, the Japanese Laid-open Utility Model Publication No. 58-7448 which is a division of the publication No. 56-140127 and was published Jan. 18, 1983. According to the Japanese publication No. 56-140127, a corner region of the casing between the top and one side wall thereof has a corner opening defined therein so as to open upwards and transversely and, hence, so as to have a top open area and a side open area. A generally L-shaped covering having top and side wall pieces is normally mounted on the casing to close the corner opening region with the top and side wall pieces closing the top and side open areas, respectively. To permit the casing to receive the L-shaped covering, side edges of the side wall confronting the side open area is formed with guide grooves so as to depict a shape similar to the shape of a figure "U" for receiving mating guide edges formed on three sides of the side wall piece of the L-shaped covering. With the L-shaped covering is in position to close the corner opening in the casing, an outer surface of the side wall piece is formed with a projection which serves concurrently as a knob and an actuating piece.
The L-shaped covering referred to above can also be utilized as a test actuator for the relay unit. In order for the L-shaped covering to be used as the test actuator, the covering then held in position to close the corner opening in the casing should be removed with an external pull applied to the knob. After the covering has been turned 180.degree. about the longitudinal axis of the side wall piece to bring the knob in position to confront the interior of the casing, the covering is then re-mounted on the casing with the side edges guided along the mating guide grooves. As the covering so remounted is seated in the side open area of the corner opening, the knob is, as the actuating piece, brought into engagement with the actuating lever and a further external push applied to the covering causes the actuating piece to urge the actuating lever. In this way, the operability of the electromagnetic relay assembly can be tested.
The Japanese publication No. 58-7448 discloses, in addition to what has been disclosed in the Japanese publication No. 56-140127, another embodiment in which mutually confronting side edges of the wall defining the side open area of the corner opening in the casing are formed with outer and inner sets of parallel guide grooves. While the outer set of the guide grooves are identical in structure and function with the guide grooves disclosed in the publication No. 56-140127, the inner set of the parallel guide grooves are utilized when the covering itself is to be used as the test actuator.
The use of the outer and inner sets of the parallel guide grooves has been intended to avoid the necessity of the covering being turned 180.degree. about the longitudinal axis thereof, such as required in the system of the publication No. 56-140127, when the covering is to be used as the test actuator. Therefore, according to this publication No. 58-7448, when the side wall piece of the covering is inserted guided along the guide grooves of the inner set, a free end of the side wall piece remote from the top wall piece pushes the actuating lever. In this instance, the projection formed on the side wall piece serves solely as the knob.
While the system of any one of the publications No. 56-140127 and No. 58-7448 should prove a substantial improvement over the then existing electromagnetic relay assemblies, to remove the covering and then to insert it again after the testing is indeed felt cumbersome and time-consuming. In addition, as is the case with any of the then existing relay assemblies, the testing of the relay assembly of any one of the publications No. 56-140127 and No. 58-7448 is performed by the application of the external push only along one direction.